During the manufacture of pharmaceuticals, for example, assuring and maintaining sterility of the process is critical. For aqueous processes, a sterile process filter unit (containing membrane material) is often placed within the process system to filter the effluent sent ultimately to a collection vessel. Steam is often used to sterilize both the product and the process equipment. However, steam can damage the process filter unit's membrane components, compromising the sterility of the system. Integrity testing of the process filter thus becomes necessary to ensure that it is operational.
Integrity testing involves flowing liquid, usually water, through the process filter to wet the membrane material therein. Once the process membrane material is wet, the water must be removed from the system. This typically requires a drain valve through which the water from the wet first filter is removed. In typical conventional systems, this valve is not protected by any microbial barrier, and therefore, is a potential point of contamination of the now sterile system. Air borne microbes can enter the system through the valve when opened for drainage.
The second step of the integrity test is to pressurize the system with a gas, usually air or nitrogen. Again, however, the gas must be exhausted upon completion.
The use of water and air in the integrity testing, and the subsequent removal of each from the filter, is problematic in conventional membrane-based fluid processing systems. The process filters used therein typically employ either hydrophobic or hydrophilic process membrane material and thus would seem to compel the resource-intensive identification, selection, and installation of a vent filter from a limited range of compatible matching discharge vent filter types. Off-line testing of the filter has been one solution to this problem, but is inefficient and costly, and doesn't ensure sterile integrity of the previously sterilized system.
It would therefore be desirable to provide a filter which allows for the use of both a hydrophilic and hydrophobic medium for integrity testing and to allow for the removal of unwanted gas or liquid from the system while maintaining a sterile barrier to the system against microbial contamination.